Refractory material and process of making same.



" lime and oxid of. iron to form a free y UNITED STATE PATENT OFFICE.

JAMES HANDY AND ROBERT M. ISHAM, OF PITTSBURGH,

ORS, BY MESNE ASSIGNMENTS, TO ALLEN S. DAVISON COMPANY,

rnNNsYLvnNLA, ASSIGN- or rrrrsnunea,

PENNSYLVANIA, A CORPORATION OF PENNSYLVAN 1A.

REFRACTORY MATERIAL AND PROCESS MAKING SAME.

No Drawing.

To all whom it may concern:

Be it known that 'we, JAMES ,0. HANDY and ROBERT M. IsHAM, citizens of the United States, and residents of Pittsbur h, in the county of Allegheny and State of PennsyL Vania, have invented certain new and useful Improvements in Refractory Materials and Processes of -Making Same, of which the following is a speci cation.

This invention relates to refractory materials and processes of making the same; and it comprises as a new material a refractory composition having the composition of a dolomitic lime with the major portion but not all of its lime removed, suflicient of such lime being left to serve with the contained silica, etc., for fiuxing purposes, such composition if necessary containin other added bonding materials such as si ic'a and iron; and it also comprises a methodof making such materials wherein dolomite or magnesian limestone is thoroughly burnt to free it of carbon dioxid and is thereafter submitted to a leaching or washing operation with cold water to remove the major portion but not all of the lime, washing being interrupted or discontinued when the extracted material shows from 3 to 10 per cent. of calcium oxid (calculated on the dried material) and wherein the material is thereafter recalcined at a temperature to give a dead. bturnt product, bonding or coating materials'being added, if desired, at the time of this recalcming operation; all as more fully hereinafter set forth and as claimed. In the operation of basic open hearth furnaces the iron is melted in a furnace chamber where it is exposed to the action of oxygen and of lime for the purpose of eliminating the impurities of acid nature, such as silicon, phosphorus and sulfur, the silicon and phosphorus so oxi ized unitin pith usi- In this operation the nature of ble slag. the lining material of the furnace is of the must have great greatest importance. v It mechanical strength and a ghood bond to re- 's'ist the washing action of t e iron and the manipulations incident to the process, and it must be as far as possible neutral or indifferent to the actions and reactions going on. be of such a nature that it will It must not flux either with the lime'and oxld of iron on the one hand or with the Specification of Letters Patent.

.inagnesian limes or kiln, etc. acid impurities of Patented July 2, 1918.

Application filed January 30, 1917. Serial No. 145,530.

other. It must be refractory to a very great degree since the temperature of operation is high. So far the best materials found for this purpose are certain ades of magnesia made from magnesite imported mainly from Austria. Magnesia after calcination is a highly refractory material and is rather inacti e chemically, such activity as it' evinces being that of a base. Its silicates have a melting point so high that magnesia has ver' little tendency to flux away with silica... Ma nesia in an ofitself does not have muc mechanical strength; it is so refractory that it cannot be caused to give a good bond in the furnace. It is for this reason that special grades of magnesia from magnesite are employed which contain more or less impurities fusible enough to give a bonding action without being suflicient in amount to detract from the refractory qualities of the magnesite. These special grades of somewhat impure the iron on the magnesia being expensive and hard to obresent, many efforts have been made to pro best substitutes so far found are calcined dolomites. Granulated hard burnt dolomitie lime is refractory enough, has but little action in the furnace and may by certain expedients be caused to give a bond when used for lining or patching a furnace. It is difficult, however, to prevent these dolomitie limes from absorbing moisture and carbonic acid when exposed to air in storage or in transit. Like pure magnesia they have little bonding action and must ordinarily be caused to bond by the addition of various other materials; as by mixing them with basic open hearth slag.

It has been found that there can be pro duced from these magnesian limestones or dolomites a refractory material which 00mbines all the desirable qualities of magnesia stated above and which is of more constant composition and properties than the stated native magnesites while it does not deteriorate on shipment or storage as do most of the commercial materials made directly from dolomitic limestone.

To this end the dolomite or magnesium limestone is first calcined in any ordinary a paratus, such as a rotary kiln, a vertical In this operation it is endeavored merely to secure a thorough calcination j This calcined material, which should not be oyerburnt,"is placed in aleaching vat or other suitable extracting apparatus and a without carryin the temperatures high as to cause the material to bedeadburnt.

The calcined material is next. treated with cold water in suflicient amount to 'sl'ake and iremoveqthe bulk .ofgthe. lime. While various chemicals. may be added to the water The water is best used as cold as possible. a

In apractical'embodiment of our process we may take a dolomite carrying, say, 45 gar cent. magnesia and calcine it in a rotary 15.

In to obtaina granulated material of a size ranging between a pin-head and a pea.

slow current of cold water passed through I. until the residual material shows some- 'where between 3j and' 10 per cent. of lime after drying and recalcining'; the precise I I f proportionoflime allowed to remain being finished materialf When the leaching has I been carried w the desired extent, the -'re 'fsfidual material is next dried" in a rotary 80 drier or other suitable form of drier; x The dried material is'next: calcined to free -it of I water of hydration and carbon dioxid.

' V f Ifithedolomitecarries small amounts of silica and iron the material: so produced is readyiiordireet] use; and it may be'simply crushed and used in the same way as='1mported impure magnesiasfi Frequently how ever,flit -is"necessary to supplement somey what'the'amoun't of silica-and iron' natu-' rally present in' obtaining a material which f wgill bond well. 1 Thed'olomite'sas a rule do f not 'Qca'rry" any great j amountof} combined i f silica,'su ch silica as is present-being largely thd foim of sand (quartz) is not very active for the present purposesu ;With

such dolomitesfit better to give f a'small add1t on"of @linaterial carrying combined; 7 silicaand' iron; [such as-bas'ic"open-*hearth b slag. The calcined'f material-' should; I carry between and 6 per-:- cent. of c'a1ciuni oxid, although 1n'some.'cases the "amount- 0h calgo as high asjlolper centa' ij a l ld "(5 to '90per' centfof'magnesiamilo seofa ( 1. 76 2 good bonding actionit s'houldalso carry i to 8 percentf of silica with l -to 4:- per centijofoxid ofironf'A'few'. er cent.

a may'also be present? I analysis shows a' deficit in the silica and iron in the aterial f it may bemade up by-the'additure should 7 vantageously be crushed to about a IO-mesh determined by the nature of the dolomite fused and the properties desired in the -t1on of .f'a littlebasicfopen hearth slag, a I [substance which contains Other materials composed of or containing ironsih'cates may be employed instead. The; proper amount of finely crushed'or powdered; basicpopen hearth slag maybe mixed with Y iron silicate.

the leacheddolomitic lime prior to the second calcination. The effort is to produce a material which shall contain 85-88 per cent. of magnesia with the rest consisting of lime in the proportion of 3 to 10 per cent. and silica in the amount of 4 to 8 per cent. anda little iron, the lime, iron and silica being uniformly distributed through. the calcined material so as to form a bond for all particles. With a less proportion of magnesia the material is not refractory enough; with a much greater proportion of'magnesia it will'not bond well. And it has been found that the presence of 3 to 10 per cent. of residual calcium oxid makes the bonding much'better while this amount is not suflicient to cause the material to slake or alter in transit and storage.

- In burnin the second time the temperafie carried high enough to produce a dead burnt material with the magnesia thoroughly shrunk and condensed. The material coming from the kiln may adsize; but it maybe delivered from the kiln in granules. of larger size with advantage formany purposes. The material com ing from the kiln ma be'crushed, molded into magnesite bricks, locks or other shapes other material as a, temporary binder during the :baking operation. Thi temporary .binder chars:--and disappears during the baking and when; the temperature becomes high: enough the impurities exercise their onding action. In the final calcination, whether this -calcination beone that 'duces' granulated; material orbe. the; reheating to produce bricks,- the. temperature should reach-from 1500'to 1550 C. The. purer the dolomite, the more basic open -hearth. slag or another permanent bonding'agent must vbeadded. ".NVhat is=claimedisqz 1 1'. Thexprocess o f making magnesia refractories, which comprises calcining dolomite extracting so as to remove the major rehe'atportion but. notall. of v the lime and ing ta producerefractory materials.

e process on makingn iagnesia refractories which com rises i calcining doloniite, extractingwith cold water toremove fliemajor, portion: but not all of-"the lime 1186i mite, 20,

tion but not a and reheating to produce refractory materials.

3. The process of making magnesia refractories which comprises calcining dolomite, extracting so as to remove the major ortlon but not all of the lime and reheatmg in the presence of small amounts of bonding material terials.

4. The process of making magnesia refractories which'comprises calcining" dolomite, extracting with cold water to remove the major ortion but not all of the lime and reheating in the presence of small amounts of bonding material to produce refractory materials.

5. The process of making magnesia refractories which comprises calcining doloextractinglime till the lime content is reduced to between 3 and 10 per cent. and reheating to produce refractory materials.

6. The process of making magnesia refractories which comprises calcining dolomite, extracting lime till the lime content is reduced to about 6 percent. and reheating to produce refracto .materials.

7. The process 0 making magnesia refractories which comprises calcining dolomite, extracting so as to remove the major portion but not all of the lime, shaping into bricks and reheating to producerefractory materials.

8. The process of making magnesia refractories which .comprises calcining dolomite, extracting with cold water to remove the major portion-but not all of the lime, shaping into bricks and reheating to produce refractory materials. a

9. The process of making magnesia refractories which comprises calcining dolomite, extractin to remove the major porl of the lime, shaping 1nto bricks and reheating in the presence of to produce refractory malinings,

small amounts of bonding material to produce refractory materials.

10. The process of making magnesia refractories which comprises calcining dolomite, extracting with cold water to remove the major portion but not all of the lime, shaping into bricks and reheatin in the presence of smallamounts of bon ing material to produce refractory materials.

11. The process of making magnesia refractories which comprises calcining dolomite, extracting lime till the lime content is reduced to between 3 and 10 per cent., shaping into bricks and reheating to produce re-' fractory materials.

12. The process of fractories which comprises calcining dolomite, extracting lime till the lime content is reduced to about 6 per cent., shaping into bricks and reheating to produce refractory materials.

13. As a new material for basic furnace linings, a refractory comprising the constituents of a water leached dolomitic lime having most of the lime removed, said re-. fractory containing between 75 and 90 per cent. magnesia, between 3 and 10 per cent. of lime and small amounts of silicia and 11'011.

14.As a new material for basic furnace a refractory brick composed of bonded granules, such granules com rising the constituents of a water leache dolomitic lime having most of the lime removed said refractory containing between 75 and 90, per cent. magnesia, between 3 and 10 er cent. of lime and small amounts of si lca and iron.

In testimony whereof, we afiix our signatures hereto.

JAMESO. HANDY. ROBT M. ISHAM.

making magnesia rep 

